Long term goals of this project are to improve our understanding of cellular and molecular mechanisms controlling the survival and differentiation of visual neurons, and to test the hypothesis that these phenomena are regulated by the interactions of visual neurons with A) their targets of innervation; b) the neurons from which they receive afferent connections; and c) the glial cells with which they are associated. It is hoped that further understanding of these developmental mechanisms will increase our chances to intervene upon injured visual neurons to promote their regeneration. Purified monolayer cultures from chick embryo neural retina or optic lobe neurons will be the basic experimental system. Neuronal differentiation will be evaluated by i) the presence of cellular machineries necessary for neurotransmitter-related activities; ii) morphological specialization of the neurons; iii) neuritic development; and iv) development of synapsis. Putative sources of regulatory influences will be retinotectal interactions (studied using co-cultures, tissue extracts of conditioned media), and glia-neuron interactions (using purified monolayers of optic lobe or neural retina non-neuronal cells). The role of substratum-attached materials in the elongation and directionality of neurites will also be studied. Molecules responsible for activities that might be detected in tissue extracts or conditioned media will be characterized and fractionated. The involvement of taurine in the regulation of survival and differentiation of cultured retina cells will be investigated. Finally, some of the properties of the cultured nonneuronal cells will be studied, particularly with respect to the high affinity uptake of neurotransmitters.